The conventional spring balance assembly used industry wide is similar to that shown in U.S. Pat. No. 3,244,440 issued to Albert A. Ashton et al on Apr. 5, 1966. This design for a spring balance counterweight system for balancing the loading arm employs a number of conventional elements, as shown in FIG. 1 of Ashton et al, including a means for mounting the spring support system to the vertical riser 10, an attachment means for attaching the spring support to the horizonal swivel 12 such as bracket 17 and an attachment arm 33 for connecting the spring support system to the loading arm. Also there is typically some form of housing, generally shown as bracket 17, which includes some means for supporting a shaft 18 or similar element which can be secured in place relative to bracket 17 by a variety of means such as cotter pins 19. A pair of spring support elements 21 and 22 are supported by shaft 18 and they are adapted to house and carry coil spring 24. Spring 24 has a pair of oppositely disposed coil end elements 25 and 27 which are designed to extend into slots 26 and 28 of spring supports 22 and 21, respectively. Spring support 22 furthermore has a rotatable arm 23 which extends outwardly and is attached to arm 33 which in turn is connected to the loading arm such that any movement of the loading arm is transmitted by arm 33 to rotatable arm 23 which in turn is connected to and moves against the resistance of spring 24. Since the spring support system may require initial adjustment and periodical readjustment in order to properly support the loading arm in the desired position, any spring assembly including the above-described Ashton system requires a means for adjustment that is capable of tensioning or relaxing the coil spring in order to estblish the desired relationship to the loading arm. To accomplish this in Ashton spring support element 23 is designed to be movable in either direction relative to the spring such that this movement will tighten or relax the spring tension on spring 24. A means is provided for locking spring support 22 such as the teeth that cooperate with set screw 29 to lock spring support 21 in a given position. A more complete description of this type of locking device is shown and described in FIGS. 2 and 7 of U.S. Pat. No. 3,038,714 issued to R. M. Klaus et al. entitled Torsional Spring Balance Unit. The toothed spring regulator 18 of Klaus forms a part of spring support element 9 and is rotatably affixed relative to shaft 17 in bracket 12. Regulator 18 is also fixed to hub 21 that has a slot 22 to receive a lock coil end 29 of tension spring 28. The regulator therefore can be used to increase or decrease the tension on spring 28 by counter-clockwise or clockwise movement, respectively and, once positioned to the desired tension, is locked in place by keeper 31.
This design allows the user to tighten or loosen coil spring 24 to the degree necessary to adequately support and position loading arm. It also allows the user to periodically readjust as required to account for spring fatigue or the like or the addition of auxiliary parts that add weight to the loading arm for alternative end uses. The Ashton design, while typical in the industry, has a number of problems such as the need for periodic retensioning and the difficulty in retensioning the spring support assembly, the difficulty in changing spring 24 to change the available weight support range, and the exposure of the several system elements to the environment. The consequence of these problems is that this system is not always reliable. For example, in order to adjust and/or readjust the spring assembly system, the operator must support the loading arm in order to relieve coil spring 24 of the load, make an adjustment to spring support 21 as best as can be guessed, and then release the loading arm hoping that the new spring tension is adequate to support the loading arm. This maneuver tends to frustrate the worker when there is frequent retensioning and inevitably the operator foregoes the retensioning procedure. The result is that the spring rapidly fatigues or loses its resiliency, the available counterbalancing spring tension diminishs and the loading arm eventually falls to or is left to rest on the ground. Furthermore the above-described spring balance system and the system typically used in the industry is unclosed and hence is unprotected and subject to further deterioration from exposure to the environment.
Accordingly it is an object of the present invention to provide a spring support system that is capable of providing high reliability and a greater useful life while still being relatively inexpensive.
Furthermore it is an object of the present invention to provide a system that is simple and convenient and that can be quickly adjusted to account for a variety of service conditions including the addition of parts to the loading arms in order that the user can readily accommodate a variety of end uses without the need for a difficult or involved method of adjustment.
Finally it is an object of the present invention to provide a system that is capable of handling a wide range of loading requirements with an infinitely variable adjustment means and by employing a series of different size springs having different load ranges which can be easily replaced to increase or diminish the available spring tension.